This invention relates to lead-acid storage batteries, and more specifically, to a lead-acid battery electrolyte fluid solution additive.
Employed in vehicle and equipment starting and traction applications, lead-acid storage batteries are the oldest, most efficient, most reliable, most economical, and most widely used rechargeable electrochemical generator worldwide. Other applications for lead-acid batteries span the range from small portable devices to large sizes as used in submarines.
Over the past fifty years, little has changed to improve the performance and life of a lead-acid battery. Most improvements have been confined to such things as battery casings. For the most part, the reason a battery fails to continue to function effectively is due to the chemical process that takes place in each cell.
Essentially, a lead-acid battery is a series of cells, or grids of both high and low antimony. The negative plate is filled with grey oxide incorporating red lead oxide Barium Sulfate, and carbon black, while the positive plate is filled with grey oxide incorporating red lead oxide or litharge. Both plates are immersed into an electrolytic solution of diluted sulfuric acid. The red lead oxide plate is the positive pole and grey lead plate is the negative pole. In each cell, the anode is porous metallic lead and the cathode is made of lead dioxide. As a battery discharges, completing the circuit, electrons are released from the anode and the resulting Pb.sup.2+ ions immediately react with SO.sub.4.sup.2- ions precipitating out insoluble lead sulfate on the surface of the electrode. At the cathode, electrons from the external circuit reduce PbO.sub.2 to water and Pb.sup.+ ions, which also immediately react with sulfate ions to precipitate PbSO.sub.4 on the electrode. The reactions are:
Anode: Pb(s)+SO.sub.4.sup.2-PbSO 4(s)+2e-
Cathode: PbO.sub.2 (s)+SO.sub.4.sup.2- +4H.sup.+ +2e-PbSO.sub.4 (s)+2H.sub.2 O(e)
Left Side Total: Pb(s)+PbO.sub.2 +2SO.sub.4.sup.2- (aq)+4H.sup.+
Both the cathode and the anode are largely converted to PbSO.sub.4 (s) when the battery is fully discharged. By applying an opposite voltage to one cell, a reverse chemical reaction occurs and that cell will recharge. Lead-acid batteries undergo several charge/discharge/recharge cycles before they become inoperable and are recycled or enter the toxic waste stream. The reason for most batteries failing to operate properly is due to this electrochemical process, battery flaking of the PbSO.sub.4, or from an internal short circuit.
As the battery discharges, the positive plate reacts with the sulfuric acid to produce lead ions and water. The negative plate simply dissolves to form lead ions in the process, which finally leads to the battery's complete failure. While charging, the positive plate builds up a thicker coating of lead oxide, migrating water, and lead ions from the sulfuric acid. As it does so, the negative plate bubbles and releases hydrogen from the sulfuric acid as it builds up a crust of lead.
It is the lead ions formed in the discharge cycle which cause problems. They agglomerate and fuse together with sulfate ions in sulfuric acid to form a highly insoluble lead sulfate. When this sulfate sediment builds a passive sediment layer on the electrodes, it reduces porous separator ionic conductivity by pore blocking and will eventually lead to cell shorting or self-discharge. The battery may well be serviceable in every other way, only the sulphation or calcification will stop the battery from operating.
Various battery additives claim to solve many of these problems mentioned above particularly, the rate of charging and starting power in hot and cold weather. U.S. Pat. Nos. 4,617,244, by Greene, 3,281,281, by Schaefer, and 3,945,849, by Hoffman, claim that a unique mixture of chelates and metal salts would increase the flow of current in the electrolyte to enhance battery performance characteristics. Although the mechanisms by which these mixtures work are undefined, the use of such a mixture could because of their known corrosive characteristics could cause accelerated decay of the lead plates leading to untimely battery failure.